Vaso-occlusive devices with in-situ stiffening

ABSTRACT

A vaso-occlusive device is constructed out of dissimilar metallic materials that are in contact or otherwise in close proximity with one another, thereby causing the device to undergo galvanic corrosion when exposed to an electrolytic medium, such as blood or other body fluid, wherein one of the dissimilar metallic materials is zirconium or zirconium alloy to create a corrosive product including zirconia having a relatively high hardness, a relatively high fracture toughness, and a relatively high stability when the device is implanted in a vasculature site, such as an aneurysm.

RELATED APPLICATION DATA

The present application is a continuation of U.S. patent applicationSer. No. 14/835,131, filed Aug. 25, 2015, which claims the benefit under35 U.S.C. § 119 to U.S. provisional patent application Ser. No.62/047,268, filed Sep. 8, 2014. The foregoing applications are herebyincorporated by reference into the present application in theirentirety.

FIELD OF THE INVENTION

The disclosed inventions pertain generally to vaso-occlusive devices forestablishing an embolus or vascular occlusion in a blood vessel.Specifically, the disclosed inventions pertain to systems and methodsfor in-situ stiffening of vaso-occlusive devices.

BACKGROUND

Vaso-occlusive devices or implants are used for a wide variety ofreasons, including treatment of intra-vascular aneurysms. Commonly usedvaso-occlusive devices include soft, helically wound coils formed bywinding a platinum (or platinum alloy) wire strand about a “primary”mandrel. The coil is then wrapped around a larger, “secondary” mandrel,and heat treated to impart a secondary shape. For example, U.S. Pat. No.4,994,069, issued to Ritchart et al., which is fully incorporated hereinby reference, describes a vaso-occlusive device that assumes a linear,helical primary shape when stretched for placement through the lumen ofa delivery catheter, and a folded, convoluted secondary shape whenreleased from the delivery catheter and deposited in the vasculature.Other vaso-occlusive devices having woven braids or embolic agents havebeen used in treatment of intra-vascular aneurysms.

In order to deliver the vaso-occlusive devices to a desired site in thevasculature, e.g., within an aneurysmal sac, it is well-known to firstposition a small profile, delivery catheter or “micro-catheter” at thesite using a steerable guidewire. Typically, the distal end of themicro-catheter will stay in a desired position for releasing one or morevaso-occlusive device(s) into the aneurysm once the guidewire iswithdrawn. A delivery or “pusher” wire is then passed through themicro-catheter, until a vaso-occlusive device coupled to a distal end ofthe delivery wire is extended out of the distal end opening of themicro-catheter and into the aneurysm. Once in the aneurysm, thevaso-occlusive devices bend to allow more efficient and completepacking. The vaso-occlusive device is then released or “detached” fromthe end delivery wire, and the delivery wire is withdrawn back throughthe catheter. Depending on the particular needs of the patient, one ormore additional occlusive devices may be pushed through the catheter andreleased at the same site.

One well-known way to release a vaso-occlusive device from the end ofthe pusher wire is through the use of an electrolytically severablejunction, which is a small exposed section or detachment zone locatedalong a distal end portion of the pusher wire. The detachment zone istypically made of stainless steel and is located just proximal of thevaso-occlusive device. An electrolytically severable junction issusceptible to electrolysis and disintegrates when the pusher wire iselectrically charged in the presence of an ionic solution, such as bloodor other bodily fluids. Thus, once the detachment zone exits out of thecatheter distal end and is exposed in the vessel blood pool of thepatient, a current applied through an electrical contact to theconductive pusher wire completes an electrolytic detachment circuit witha return electrode, and the detachment zone disintegrates due toelectrolysis.

When the above-mentioned vaso-occlusive devices are placed within ananeurysm, they tend to induce a formation of thrombi for occlusion ofthe aneurysm. However, once the above-mentioned vaso-occlusive devicesare delivered into an aneurysm, they may not have sufficient strength orstiffness to retain their shape within the aneurysm.

For example: U.S. Pat. No. 6,015,424 (Rosenbluth et al.) describes anocclusive device having a series of flexible chain-like segmentsincluding a metallic material, such as platinum or tungsten. Through theapplication of an externally-sourced current, the metallic materialfuses the inter-linked segments together by electrolytic corrosion. Thiselectrolytic corrosion may cause a temporary, relative stiffening of thedevice. However, the corroded device also tends to quickly degrade withtime, and with the influence of hemodynamic forces and thrombolyticprocesses, the corroded, degraded device will tend to move or changeshape, e.g., through the process of seeking a minimally energeticmorphology, may move out of the position in which it was originallyplaced.

By way of another example, U.S. Pat. No. 8,556,927 (Dehnad) describes avaso-occlusive coil having a first metallic material in the form ofplatinum or platinum alloy, and a second metallic material in the formof zinc or zinc alloy, so that a chemical reaction is initiated creatinga galvanic cell when the coil is deployed in an aneurysm due to thepresence of electrolytic blood. Again, this galvanic corrosion may causea temporary, relative stiffening of the device, the corroded device willalso tend to quickly degrade with time and the influence of hemodynamicforces and thrombolytic processes, and tends to move or change shapeafter placement. In some cases, the delivered vaso-occlusive devices mayeven dislodge out of the sack of an aneurysm. Such difficulties canundesirably increase the time needed for performing a medical procedure,as well as further increase the risk of a thrombus formation in anunintended location in the blood vessel, as the vaso-occlusive devicesmigrate out of the aneurysm.

Accordingly, it would be desirable to provide vaso-occlusive deviceshaving a more durable stiffness and structural integrity to retain theirshape and position over time at a target location (e.g., within ananeurysm), minimizing undesired migrations and collapsing.

SUMMARY

In accordance with a general aspect of the disclosed inventions, avaso-occlusive device is constructed out of dissimilar metallicmaterials that are in contact or otherwise in close proximity with oneanother, with one of the metallic materials being zirconium or zirconiumalloy, thereby causing the device to undergo galvanic corrosion whenexposed to an electrolytic medium, such as blood or other body fluid, tocreate a corrosive product including zirconium dioxide (“zirconia”) whenthe device is implanted in a vasculature site, such as an aneurysm.

In various embodiments, the device is constructed from a plurality ofwire members that are braided together or otherwise arranged into avariety of different structures and shapes suitable for use as avaso-occlusive embolic device. For example, the device may comprise atubular sleeve, or a coil configuration. By way of another example, thedevice (e.g., a braid) may be provided as an adjuvant component that atleast partially surrounds and covers a separate (e.g., conventional)vaso-occlusive device. The individual wire members may be composed of asingle metallic material (i.e., one of the dissimilar metals), or may beformed from a composition of materials, including but not limited to oneor both of the dissimilar metals. The individual wire members may varyin length, stiffness, cross-sectional shape, size, or other physicalattributes. By way of non-limiting example, individual wire members mayhave circular or non-circular cross-sectional shapes, such asrectangular or triangular cross-sectional shapes. For instance, some orall of the individual wire members may be flat ribbon wires. In someembodiments, individual wire members have irregular, non-uniformcross-sections that vary along the length of the wire members.

In some embodiments, the device is constructed from a plurality ofmetallic wire members including a first subset of wire members made fromor otherwise including platinum or platinum alloy, and a second subsetof wire members made from or otherwise comprising zirconium or zirconiumalloy, wherein the resulting electrochemical potential differencebetween platinum and zirconium forms zirconia at a plurality of contactpoints, thereby stiffening the vaso-occlusive device when exposed toblood and other body fluid after implantation. In such embodiments, thesubset of platinum or platinum alloy wires may be braided or otherwisearranged with the subset of zirconium or zirconium alloy wires so thatgalvanic corrosion formation of zirconia at the respective contactpoints occurs over time, resulting in a “progressive” in-situ stiffeningof the device.

In some embodiments, a vaso-occlusive device comprises a metallic braidformed from a plurality of wire members, each wire member having aninner core material comprising a first metallic material that is atleast partially coated, plated, or otherwise covered with an outercoating comprising a dissimilar metallic material. In one suchembodiment, the inner core material comprises platinum, and the outercoating comprises zirconium or zirconium alloy. In another suchembodiment, the inner core material comprises zirconium or zirconiumalloy, and the outer coating comprises platinum. In yet another suchembodiment, a first subset of the plurality of wire members haveplatinum or platinum alloy cores with zirconium or zirconium alloycoatings, and a second subset of the plurality of wire members havezirconium or zirconium alloy cores with platinum or platinum alloycoatings. In all such embodiments, the formation of zirconia occursalong and over the plurality of wire members, since the entire length ofeach wire member comprises both platinum and zirconium. A thickness ofthe coating material may be selected based upon a desired amount ofgalvanic corrosion and corrosion products to be produced. Further, thecoating material may be porous, wherein a pore size and/or pore densityof the coating material is selected based upon a desired amount ofgalvanic corrosion and corrosion products to be produced. In anotherembodiment of the disclosed inventions, a vaso-occlusive coil is woundfrom a wire member comprising a core made from a first metal or metalalloy acting as an electrolytic anode, and a coating made from asuitable dissimilar metallic material acting as electrolytic cathode.

Other and further aspects and features of embodiments of the disclosedinventions will become apparent from the ensuing detailed description inview of the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-B are perspective views of a vaso-occlusive device braidconstructed according to various embodiments of the disclosedinventions.

FIGS. 2A-E are perspective and cross-sectional views of a vaso-occlusivedevice braid constructed according to further embodiments of thedisclosed inventions.

FIGS. 3A-E are cross-sectional views of a vaso-occlusive coilconstructed according to various embodiments of the disclosedinventions.

FIGS. 4A-I are sectional views of vaso-occlusive devices constructedaccording to additional and alternative embodiments of the disclosedinventions.

FIGS. 5A-F are sectional views of vaso-occlusive devices constructedaccording to still further additional and alternative embodiments of thedisclosed inventions.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

Various embodiments of the disclosed inventions are describedhereinafter with reference to the figures. The figures are notnecessarily drawn to scale, the relative scale of select elements mayhave been exaggerated for clarity, and elements of similar structures orfunctions are represented by like reference numerals throughout thefigures. It should also be understood that the figures are only intendedto facilitate the description of the embodiments, and are not intendedas an exhaustive description of the invention or as a limitation on thescope of the invention, which is defined only by the appended claims andtheir equivalents. In addition, an illustrated embodiment of thedisclosed inventions needs not have all the aspects or advantages shown.An aspect or an advantage described in conjunction with a particularembodiment of the disclosed inventions is not necessarily limited tothat embodiment and can be practiced in any other embodiments even ifnot so illustrated.

In accordance with a general aspect of the disclosed inventions, avaso-occlusive device is constructed out of dissimilar metallicmaterials that are in contact or otherwise in close proximity with oneanother, thereby causing the device to undergo galvanic corrosion whenexposed to an electrolytic medium, such as blood or other body fluid,wherein one of the dissimilar metallic materials is zirconium orzirconium alloy in order to create a corrosive product comprisingzirconium dioxide (“zirconia”) having a relatively high hardness, arelatively high fracture toughness, and a relatively high stability whenthe device is implanted in a vasculature site, such as an aneurysm.

FIGS. 1A-B illustrate a vaso-occlusive device 10 constructed inaccordance with various embodiments of the disclosed inventions. Thevaso-occlusive device 10 comprises a metallic braid 12 formed from aplurality of elongate members (e.g., wires) 14 composed of or otherwiseincluding zirconium or an alloy of zirconium, along with a dissimilarmetallic material, such as platinum. The metallic braid 12 may have avariety of different shapes, sizes, lengths, etc., suitable for use as avaso-occlusive device. For example, the metallic braid 12 may comprise atubular sleeve, a coil configuration, or the braid 12 may be an adjuvantcomponent that at least partially surrounds and covers a separate (e.g.,conventional) vaso-occlusive device (FIGS. 5A-F). Individual members(hereinafter, “wire members”) 14 that are woven together to form thebraid 12 may be formed from a single material, such as one of thedissimilar metals, or may be formed from a composition of materials,including (but not limited to) one or both of the dissimilar metals. Thelength, stiffness, cross-sectional shape and/or size or other physicalattribute may differ between individual wire members 14. By way ofnon-limiting example, individual wire members 14 may have circular ornon-circular cross-sectional shapes, such as rectangular or triangularcross-sectional shapes. For instance, some or all of the individual wiremembers 14 may be formed from flat ribbon wires. Furthermore, individualwire members 14 may have irregular, non-uniform cross-sections that varyalong the length of the wire member.

In one embodiment, the individual wire members 14 of the metallic braid12 include a first subset of wire members 16 formed out of or otherwiseincluding platinum, and a second subset of wire members 18 formed out ofor otherwise including zirconium. The respective platinum (Pt) wiremembers 16 and zirconium (Zr) wire members 18 are braided, inter-woundand/or otherwise arranged so that the Pt and Zr material is in physicalcontact or close proximity at each of a plurality of contact points 20on the device 10. It will be appreciated that the dissimilar Pt and Zrmetallic materials have distinct electrochemical potentials, causing thedevice 10 to undergo galvanic corrosion at each of the contact points 20when exposed to an electrolytic medium, such as blood, or other bodyfluid. More specifically, the Pt material will act as an electrolyticcathode, and the Zr material will act as an electrolytic anode, tothereby create a respective galvanic cell at each contact point 20.These galvanic cells undergo electrochemical corrosion in the presenceof electrolytic blood after delivery of the device 10 to a targetlocation within a patient's vasculature, e.g., within an aneurysm.During the galvanic corrosion, a resulting electrochemical potentialdifference between Pt and Zr develops an electric current thatelectrolytically oxidizes and expands the zirconium, forming a corrosiveproduct zirconium oxide, ZrO₂ (“zirconia”) 70 at each contact point 20,thereby stiffening the vaso-occlusive device 10 in-situ. As furtherdescribed herein, the braided Pt and Zr wires 16 and 18 are preferablyconstructed and/or otherwise arranged relative to each other so that thegalvanic corrosion formation of zirconia at the contact points 20 occursover time, resulting in a “progressive” in-situ stiffening of the device10.

It will be appreciated that the particular selection of Zr for the anodematerial resulting in the formation of zirconia as the corrosive productis highly advantageous, since zirconia comprises a relatively highhardness (about 8.5 Moh's hardness), a relatively high fracturetoughness, and is also a highly stable, relatively non-degradablematerial in blood and other biological fluids. As such, the formation ofzirconia at the respective contact points 20 creates a substantiallymore durable stiffness and over-time strength of the vaso-occlusivedevice 10, minimizing undesirable migrations and other disadvantagesattributed to a relatively low and/or temporal stiffness, and relativelyfast degradation, respectively, of the devices disclosed in Rosenbluthet al. and Dehnad.

It will be appreciated that the dissimilar metallic material acting aselectrolytic cathode to the zirconium anode may include a number ofsuitable metallic materials, such as, platinum, iridium, platinumalloys, platinum-tungsten alloy, platinum-iridium alloy, platinumrhenium alloy, platinum palladium alloy, or the like, or suitablecombinations thereof. In some embodiments, yttrium may be introduced asan additive to zirconium to form a zirconium-yttrium alloy to be used asone of the dissimilar metallic materials. During galvanic corrosionprocess, the corrosion product not only contains zirconium dioxide(zirconia), but also yttrium oxide (“yttria”). The presence of yttria inthe zirconia corrosion product further stabilizes the zirconia andenhances fracture resistance of the implanted occlusive device. In stillother embodiments, elements including (without limitation) calcium,cerium, aluminum, titanium, and hafnium may be added to the zirconium sothat calcia, ceria, alumina, or hafnia, respectively, is also formedduring the galvanic corrosion process to enhance the stabilization andfracture resistance of the zirconia.

FIGS. 2A-E illustrate alternative embodiments of a vaso-occlusive device10′ constructed in accordance with the disclosed inventions. For ease inillustration and disclosure, the features and configurations of device10′ that are the same as device 10 of FIGS. 1A-B are given the samereference numerals. The vaso-occlusive device 10′ comprises a metallicbraid 12′ formed from a plurality of wire members 14′, each wire member14′ having an inner core material 26, preferably one of Pt and Zr, thatis at least partially coated, plated, or otherwise covered with an outercoating material 28, preferably the other one of Pt and Zr. Thethickness 29 of the coating material 28 can be varied, depending on thedesired amount of galvanic corrosion and corrosion products to beproduced (FIGS. 2C-D). The coating material can be porous (or“microporous”), wherein the pore size and pore density of the coatingmaterial are (again) determined by the desired amount of galvaniccorrosion and corrosion products to be produced.

By way of non-limiting example, the core material 26 may be composed ofPt or Pt alloy, which acts as the electrolytic cathode, and the coatingmaterial 28 may be composed of Zr or Zr alloy, which acts as theelectrolytic anode. Alternatively, the core material 26 may be theelectrolytic anode composed of Zr or Zr alloy, and the coating material28 may be the electrolytic cathode composed of Pt or Pt alloy. In astill further alternative embodiment shown in FIG. 2B, the metallicbraid 12′ is formed of a first plurality of wires 16′, each wire 16′having an electrolytic cathode core 26 composed of Pt or Pt alloy, andan electrolytic anode coating 28 composed of Zr or Zr alloy, and asecond plurality of wires 18′, each wire 18′ having an electrolyticanode core 26 composed of Zr or Zr alloy, and an electrolytic cathodecoating 28 composed of Pt or Pt alloy. With each of these embodiments,when the vaso-occlusive device 10′ is delivered into an aneurysm and isexposed to blood, the dissimilar metallic Pt and Zr materials undergo aprogressive galvanic corrosion, forming zirconia as the corrosiveproduct 70 on the respective wires 16′ and 18′ (collectively, wires14′), thereby stiffening the vaso-occlusive device 10′ in-situ. Theformation of zirconia in the embodiment illustrated in FIG. 2E occursalong and over the plurality of wires 14′ themselves, in addition to thecontact points 20, since the entire length of each wire of the plurality14′ comprises both Pt and Zr.

By way of another example, FIGS. 3A-E illustrate a vaso-occlusive coil50, constructed in accordance with the disclosed inventions. FIGS. 3B-Eare cross sectional views of a portion of the coil 50 of FIG. 3A. Thecoil 50 may be made from a metal, such as pure platinum (Pt). In otherembodiments, the coil 50 may be made from an alloy, such asplatinum-tungsten alloy (Pt/W), e.g., 8% tungsten and the remainderplatinum (Pt). In further embodiments, the coil 50 may be made fromplatinum-iridium alloy, platinum rhenium alloy, platinum palladiumalloy, or any suitable metallic material suitable for forming theelectrolytic cathode. The coil 50 further comprises a coating 60 made ofzirconium or zirconium alloy acting as electrolytic anode (FIG. 3C). Inalternative embodiment, the coil may be made from a neutral material,such as a polymer, with a coating 60′ composed of zirconium and platinum(FIG. 3D). The dissimilar metallic materials of the coil 50 (cathode)and coating 60 (anode) (FIG. 3C) or coating 60′ (cathode/anode) (FIG.3D) have distinct electrochemical potentials to undergo a progressivegalvanic corrosion (FIG. 3E), when exposed to an electrolytic mediumsuch as blood to thereby expand and create corrosive products 70 thatcause in-situ stiffening of the coil 50 in target location, e.g., withinan aneurysm.

FIGS. 4A-I illustrate various vaso-occlusive devices 90 constructed inaccordance with the disclosed inventions. The vaso-occlusive devices 90include exemplary arrangements and/or configurations including aplurality of coils 50, such as those shown in FIGS. 3A-E and describedabove, each coil 50 being formed from dissimilar metallic materialsincluding zirconium or zirconium alloy that are placed into contact orsufficiently close proximity so as to corrode and create expandingoxides and corrosive products including zirconia 70 when exposed to anelectrolytic medium, such as blood. Because each contact of twodissimilar metals in the present of blood can form a respective galvaniccell, the coatings 60 may contain numerous individual galvanic cells.Expansion of corrosion material takes up the space between the coils 50,leading to an increase in packing density and in-situ stiffening of thepacked coils 50, e.g., after placement of the device 90 within ananeurysm. The degree of the expansion can be optimized based on theapplication and coating properties, such as material selection, coatingthickness, and microstructure. Since the galvanic corrosion occurs overtime, the in-situ stiffening of the coils 50 is progressive.

FIGS. 4A-B illustrate a vaso-occlusive device 90 having a layered coilconfiguration, in which an inner coil 52 is coaxially disposed within anouter coil 54 lumen 55. At least one of coils 52 or 54 is composed ofdissimilar metallic materials (e.g., Pt and Zr), including coatings 60,as described above in coil 50. In one embodiment, both coils 52 and 54comprise at least two dissimilar metallic materials (e.g., Pt and Zr) toundergo the galvanic corrosion when exposed to an electrolytic medium,so that the vaso-occlusive device 90 is progressively stiffened andadditionally bonded in-situ (FIG. 4B).

FIG. 4C illustrates an alternative embodiment of the device 90 having anadjacent member 65, e.g., a tubular member, braided layer, stent, coil,or the like, disposed over the outer coil 54 and covering the layeredcoil configuration. When the galvanic corrosion occurs, the anodematerial of the vaso-occlusive device 90 expands, creating corrosiveproducts 70 and causing compression 75 to the adjacent member 65, whichleads to in-situ stiffening and further bonding of the device 90.

FIGS. 4D-E illustrate another alternative vaso-occlusive device 90having a layered coil configuration, in which a first coil 56 isadjacently disposed from a second coil 58 (e.g., parallel or lateral).At least one of coils 56 or 58 is composed of dissimilar metallicmaterials and/or having the coatings 60, as described above with respectto coil 50. In one embodiment, each of the coils 56 and 58 comprise thecoating 60′ including two dissimilar metallic materials (e.g., platinumand zirconium). When the vaso-occlusive device 90 is exposed toelectrolytic blood when placed in the vasculature, it undergoes galvaniccorrosion creating the corrosive products 70, creating in in-situstiffening and bonding of the coils 56 and 58.

FIGS. 4F-G illustrate still another alternative vaso-occlusive device 90having a layered coil configuration with a plurality of coils, includinga first coil 57 composed of an electrolytic anode material, e.g., Zr,disposed between at least two additional coils 59 composed of anelectrolytic cathode material, e.g., Pt. During galvanic corrosion afterplacement in the vasculature, a resulting electrochemical potentialdifference develops an electric current that electrolytically oxidizesand expands the Zr anode coil 57 forming zirconia as a corrosion product70 between the two Pt cathode coils 59, thereby stiffening and bondingthe vaso-occlusive device 90 in-situ (FIG. 4G).

FIGS. 4H-I illustrate yet another alternative vaso-occlusive device 90having a plurality of coils in a layered coil configuration, in whichthe cathode coil 59 is coaxially disposed within the lumen 55 of ananode coil 57. The vaso-occlusive device 90 further includes theadjacent member 65 disposed over the outer anode coil 57. Similar to theembodiment illustrated in FIG. 4C, when the galvanic corrosion occurs inFIG. 4I, expansion of the vaso-occlusive device 90 due to the corrosiveproducts 70 causes compression 75 to the adjacent member 65, resultingin progressive in-situ stiffening and bonding of the vaso-occlusivedevice 90.

FIGS. 5A-F illustrate additional vaso-occlusive devices 100 constructedin accordance with the disclosed inventions. The vaso-occlusive devices100 may include a braid 101 to further strengthen the in-situ stiffeningof the devices 100 and retain the corrosion products 70 formed by thegalvanic corrosion of the dissimilar metallic materials includingzirconium or zirconium alloy. The corrosion products 70 formed with, on,or around the braid 101 would further support the in-situ stiffeningefficiency of the vaso-occlusive devices 100. It will be appreciatedthat having a braid in the vaso-occlusive devices 100 would increase theamount of galvanic corrosion cells, since the braid creates more surfaceareas. After galvanic corrosion, the braid would become stiffer as thecontact points of the wires forming the braid would be fixed in place bythe corrosion products including zirconia 70, thus strengthening thevaso-occlusive devices 100 in-situ. The braid 101 may be composed ofsuitable biocompatible materials. Alternatively, braids 10 and 10′ ofFIGS. 1A-2E may be used in the vaso-occlusive devices 100 of FIGS. 5A-F.

The vaso-occlusive device 100 of FIGS. 5A-B includes at least onevaso-occlusive coil 50, and at least one braid, 10, 10′ or 101. When thebraid 101 is used in the vaso-occlusive device 100, the coil 50 includesthe at least two dissimilar metallic materials, for example in thecoating 60, to undergo galvanic corrosion. In other embodiments, one orboth of the coil 50 and braid 10, 10′ include the at least twodissimilar metallic materials, for example, in coatings 60 and 28,respectively, to undergo galvanic corrosion and thereby cause in-situstiffing of the vaso-occlusive device 100. As with the above-describedembodiments, the metallic material forming the electrolytic anode iszirconium or zirconium alloy.

FIGS. 5C-D illustrate another alternative vaso-occlusive device 100having at least two braids, an inner braid 10, 10′ coaxially disposedwithin an outer braid 101. In alternative embodiments, the outer braidmay also include the at least two dissimilar metallic materials, or justthe outer braid may include the at least two dissimilar metallicmaterials (not shown). FIGS. 5E-F illustrate another alternativevaso-occlusive device 100 having the occlusive device of FIG. 5Acoaxially disposed with the braid 101. The vaso-occlusive devices 100 ofFIGS. 5D and 5F may further include the adjacent member 65 disposed overthe outer braid 101. As with the above-described embodiments, themetallic material forming the electrolytic anode in the vaso-occlusivedevices 100 of FIGS. 5D and 5F is zirconium or zirconium alloy. Thus, aswith the embodiment illustrated in FIG. 4C, when the galvanic corrosionoccurs in FIGS. 5D and 5F, expansion of the vaso-occlusive device 100 bythe corrosive zirconia product 70 causes compression 75 to the adjacentmember 65 leading to the in-situ stiffening and bonding of thevaso-occlusive device 100.

Although particular embodiments have been shown and described herein, itwill be understood by those skilled in the art that they are notintended to limit the present inventions, and it will be obvious tothose skilled in the art that various changes and modifications may bemade (e.g., the dimensions of various parts) without departing from thescope of the disclosed inventions, which is to be defined only by thefollowing claims and their equivalents. The specification and drawingsare, accordingly, to be regarded in an illustrative rather thanrestrictive sense. The various embodiments shown and described hereinare intended to cover alternatives, modifications, and equivalents ofthe disclosed inventions, which may be included within the scope of theappended claims.

What is claimed is:
 1. An implantable vaso-occlusive device, comprising:a first plurality of metallic members comprising a first metallicmaterial; and a second plurality of metallic members comprisingzirconium or zirconium alloy that is electrochemically dissimilar to thefirst metallic material, wherein the device is constructed such thatrespective metallic members of the first plurality contact respectivemetallic members of the second plurality at respective discrete contactpoints, thereby causing the device to undergo galvanic corrosion at eachof the contact points when exposed to blood and/or other body fluid, thefirst metallic material being selected to create a corrosive productcomprising zirconia after the device has been implanted in avasculature.
 2. The vaso-occlusive device of claim 1, wherein the firstmetallic material comprises platinum or platinum alloy, and wherein aresulting electrochemical potential difference between the platinum orplatinum alloy and the zirconium or zirconium alloy forms zirconiumoxide at each contact point, thereby stiffening the vaso-occlusivedevice when exposed to blood and/or other body fluid after beingimplanted in the vasculature.
 3. The vaso-occlusive device of claim 2,wherein the first metallic material comprises one of platinum-tungstenalloy, platinum-iridium alloy, platinum-rhenium alloy, andplatinum-palladium alloy, and wherein the zirconium alloy comprises oneof zirconium-cerium alloy, zirconium-yttrium alloy, zirconium-titaniumalloy, zirconium-aluminum alloy, zirconium-calcium alloy, andzirconium-hafnium alloy.
 4. The vaso-occlusive device of claim 1,wherein the respective metallic members of the first plurality and ofthe second plurality comprise metallic wires arranged in a braidedconfiguration.
 5. The vaso-occlusive device of claim 4, wherein thebraided configuration comprises a tubular sleeve configuration.
 6. Thevaso-occlusive device of claim 4, wherein at least one wire of the firstplurality varies with at least one wire of the first or second pluralityin one or more of a length, a stiffness, a cross-sectional shape, and asize.
 7. The vaso-occlusive device of claim 4, wherein at least one wireof the first or second plurality has a non-circular cross-sectionalshape.